YOU SAID:

i am going to the store to buy sushi for my sister

INTO JAPANESE

私は妹のために寿司を買うために店に行きます

BACK INTO ENGLISH

I go to the store to buy sushi for my sister

INTO JAPANESE

私は妹のために寿司を買うために店に行きます

BACK INTO ENGLISH

I go to the store to buy sushi for my sister